Flywheel help!

[Jake_C_]

So apparently the flywheel I bought was not the right size. After doing some reading it says that 350 motors use a 12” flywheel but the one for the automatic and the new one I bought are both 14”. And it has to be 14” or it won’t work with my starter. The inside hole diameter on my new flywheel is bigger than on my old one. Here’s some pictures for reference:



The bolt pattern is also too big. I’m trying to find the right part but I’m having trouble, any help is much appreciated. I was hoping to get this done today.

 

[MEMO43]

What year is your motor
I had the same issue when a did a motor swap
I bought one for an 83 k5 series
The vehicle was a 76 it.
I got mine from orileys at the time

 

[K5Devil]

sbc 400 uses the 14” with 168 teeth

350 uses 12.75” with 153 teeth

sounds like you need a 153 tooth flywheel. But grab the casting mark off the engine so I can figure out what engine you have.

 

[K5Devil]

Count the number of teeth off the flex plate you removed as well.

 

[Bent77]

Hang on a sec, I have the part number for a one piece seal 14" plate....

 

[Bent77]

fits a 90 k5

168 tooth, takes a 12" clutch plate
https://www.oreillyauto.com/detail/...bdf6875/power-torque-flywheel/nfw1023/4672032

 

[K5Devil]

1986+ Sbc used 14” flywheel? Crazy, just learned me something new. I thought only the 400 used a 14”

 

[Bent77]

1986+ Sbc used 14” flywheel? Crazy, just learned me something new. I thought only the 400 used a 14”

Both my 72 and 77 had factory 14” flywheel. Both 350

 

[K5Devil]

Both my 72 and 77 had factory 14” flywheel. Both 350

Yep you’re not wrong.

 

[Bent77]

Yep you’re not wrong. View attachment 332229

That is a nice chart. The disc I have sitting in the garage looks to be the 11.85" spec, and was a replacement spec LUK purchased in 98 or so for the 77.
Good info

 

[K5Devil]

It’s just crazy to me that every SBC that’s been through my hands was a 12.75” haha

 

[Bent77]

Car clutch

 

[K5Devil]

Car clutch

yep. A lot of car engines. Not many truck engines.

 

[Bent77]

Most car clutches have a shallow bell housing because of the floor, where as the trucks are "deeper"

 

[Jake_C_]

Wow guys thanks so much for the help. So the old automatic flywheel is a 168 tooth wheel 14”. The new manual flywheel I bought is also a 168 14”. So the only difference is the inside hole diameter and the bolt pattern. It looks like @Bent77 got me the right part number and it’s in stock at the closest O’Reillys. I assume my motor is an 88. I’ll have to check the block sometime and find out for sure. I was confused because I was finding 12” flywheels that appeared to have the right size hole and bolt pattern and were also 168 tooth. I thought maybe that’s the size of the clutch surface and maybe the ring gear was still 14” but there was no way for me to know. You guys saved me I appreciate it. @K5Devil

 

[Jake_C_]

Also I do have a 1 piece rear main seal

 

[Bent77]

Wow guys thanks so much for the help. So the old automatic flywheel is a 168 tooth wheel 14”. The new manual flywheel I bought is also a 168 14”. So the only difference is the inside hole diameter and the bolt pattern. It looks like @Bent77 got me the right part number and it’s in stock at the closest O’Reillys. I assume my motor is an 88. I’ll have to check the block sometime and find out for sure. I was confused because I was finding 12” flywheels that appeared to have the right size hole and bolt pattern and were also 168 tooth. I thought maybe that’s the size of the clutch surface and maybe the ring gear was still 14” but there was no way for me to know. You guys saved me I appreciate it. @K5Devil

Was easy to find, had the box sitting on the shelf

 

[Bent77]

Also I do have a 1 piece rear main seal

Yes

 

[TreeFarm]

I was confused because I was finding 12” flywheels that appeared to have the right size hole and bolt pattern and were also 168 tooth. I thought maybe that’s the size of the clutch surface and maybe the ring gear was still 14” but there was no way for me to know. . @K5Devil

Right, 12" 168 tooth flywheels are referring to the clutch disk size.

Its easier to think of flywheels as 168t or 153t. the truck or car sizes respectively. They will interchange on the back of the motor as long as you have the one for the rear main seal style of your engine and you have the right bell housing and starter to fit.

The problem you ran into is you picked up a two piece rear main flywheel for your one piece rear main engine.

 

[TJ1978]

What years were the 1 and 2 piece rear main seal?
Didnt it change in 80’s to 2 piece